Since a few years, energy utilities are facing business model disruptions: grid parity of renewable technologies, stable or decreasing demand - especially in the EU -, acceleration of digital innovations within the smart-home market, uncertain policy directives and influential customers' opinions. If, in the past, the lack of entrepreneurial culture within large companies has caused losses of market shares towards smaller, innovative, more digitally mature companies or energy co-operatives, since the last 2-4 years, some utilities have been exploring pathways to fit the energy services demand of customers, in parallel to the requirements from investors and regulators. In this investigation, after a summary of the current status of the energy transition in the EU, emerging business models for the future utility are presented, in a tentative of drawing an updated overview of the current market mutations. The emerging role of the electric energy storage systems within the studied business models is detailed, including the illustration of specific pilot cases, for which technical and economic information are compared.
Solid biomass ash related issues and adequate fuel characterization, especially for fuels with similar thermochemical properties, are still major challenges in combustion. As a consequence, the fuel switching and the valorization of unconventional available fuels are hazardous. An integrated strategy to characterize biomass fuels for ash related issues is applied to four residual woody fuels, namely, a mesquite wood mixture, rubberwood, an invader bush wood, and bamboo wood. The characterization is performed with detailed analyses including (i) ash composition, (ii) ash association forms by leaching, (iii) recently reviewed predictive correlations, (iv) thermochemical equilibrium computations to predict the ash phases formed as a function of the combustion parameters and with the use of a state-of-the-art oxide database, and (v) experimental testing in a 100 kWth circulating fluidized bed pilot reactor (CFB100). The CFB100 testing allowed investigation of the fuel ash cycle including fly ash recirculation, agglomeration and fouling tendencies, and the use of halloysite and kaolin mineral additives. Among the four fuels, bamboo evidenced the higher agglomeration trend, which increased when reducing the additive. With respect to the other fuels, rubberwood seems to have a slightly higher tendency to initiate the coating-induced agglomeration mechanism. Concerning fouling, the mesquite mixture wood is more prone to deposition, mainly because of the formation of Ca-based deposits, while for the other three fuels, ash partitioning shows that the majority of reactive alkali metals fed to the pilot is accumulated in the bottom ash and circulating material. The novel integrated strategy is successfully applied for advanced solid biomass fuel characterization for combustion.
In the recent years, a growing interest for low - quality biomass fuels is observed, in both small- and large-scale combustion plants. Such fuels include wood mixtures and forest residues, short-rotation energy crops, herbaceous biomass (e.g. straws) and agricultural or fruit residues. The combustion of these fuels often portends technical operational issues, which include agglomeration of inorganic particles in fluidized beds and ash slag formation in combustors. A simplified fuel characterization approach has been developed in this work, with the objective to define the agglomeration and slagging propensity of biomass fuels for their use in combustion boilers. Among the variables that influence these complex mechanisms, the fuel inorganic composition is considered in this model. The outcome of the model is a parameter in the range 0 - 100 that indicates the specific fuel propensity to induce agglomeration and slagging issues in combustion applications. The model outcomes are validated with experimental results from literature and from laboratory tests in a pilot circulating fluidized bed reactor. The developed tool is build to be used for screening and preliminary selection of solid biomass fuels for combustion.
According to the European Biomass Association, bioenergy represents about 60% of the EU’s total consumption of renewables. The EERA Bioenergy, section of the European Energy Research Alliance, indicates that agricultural residues and non-food crops should be used at farm- and village- scales, while low quality biomass and waste could be used for medium- and large- scale power and CHP plants. Among the barriers that hamper the efficient processing of solid fuels in thermal processes, such as combustion and gasification, ash related issues are still challenging for plant operators. These issues include agglomeration in fluidized bed combustion, slag formation, and fouling of convective heat exchangers. Furthermore, advanced characterization methods for solid biomass fuels, especially predictive approaches for ash related issues, are not fully developed. Consequently, the use of unconventional biomass solid fuels is limited because of operating risks. In addition, the availability of the detailed chemical analyses of unconventional fuels is often limited. In this investigation, a validated fuel characterization tool to define the agglomeration - slagging propensity of biomass fuels for their use in thermal processes, is applied to an advanced database of mediterranean (Greece, Italy, Spain) opportunity fuels. The database is built by means of an extensive literature review, including the detailed ash chemical compositions. The input of the tool is the specific fuel ash chemical composition, and the output is the agglomeration - slagging propensity computed as a parameter in the range (0 – 100). In this work it is shown that a high ash fusion temperature (from the Ash Fusion Test) is a necessary but not sufficient condition to low agglomeration and slagging in combustion applications. Among the fuels analyzed, wood, shrubs and citrus industry agro-residues evidenced a low-to-medium median propensity to agglomerate and slag, contrarily to the high propensity of agro-residues (various), wine industry residues, and crops. About 20 opportunity fuels, with low-to-medium agglomeration and slagging propensity and for which environmental, economic and social sustainability has to be further explored, are suggested for thermal applications. Some countermeasures to efficiently process the more challenging fuels are mentioned, including the use of specific combustion additives.
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